1. Field of the Invention
The invention relates to a middle electrode with precious metal reinforcement, especially a spark plug electrode with a platinum tip and a process for producing a middle electrode.
2. Description of the Related Art
Middle electrodes with precious metal reinforcement are used preferably for spark plugs for high voltage ignition, the reinforcement being accomplished, for example, by the insertion of precious metal spheres, plates, or pins into the middle electrode by welding. A disadvantage arises in that the production of the individual precious metal pieces and their introduction into the middle electrode are very complex in terms of process engineering.
Another disadvantage arises in that the precious metal/nickel alloy welding zone, which is conventionally the base of generic middle electrodes, is exposed to hot gas corrosion and spark erosion so that the resulting damage limits the expected service lifeof the electrode.
The object of the invention is to make available middle electrodes and processes for their production, which surmount the defects which are known from the prior art. In particular, the middle electrodes will have a high service life expectation, good cold starting properties, and low voltage demand even after long engine running times.
The object of the invention is achieved by a process for producing a middle electrode with precious metal reinforcement, comprising the steps of: providing a middle electrode with an ignition tip, tapering the ignition tip relative to a body of the middle electrode, welding flat a precious metal wire with a cross section which corresponds to the tapered ignition tip onto the tapered ignition tip, and cutting the precious metal wire off at the desired height with a sharp edge. The object is also achieved by a middle electrode with precious metal reinforcement, wherein the middle electrode has a tapered ignition tip, comprising: a precious metal wire with a section with a face side, the wire is bordered on the face side by sharp edges, the section is welded flat, and an alloy area around the area of a contact of the precious metal wire section with the tapered ignition tip, the alloy area extending annularly between the precious metal and the material of the ignition tip of the middle electrode.
The invention is explained in detail with reference to the accompanying drawings.